Web service - Content is not allowed in prolog

Error:

When I try to send a file as a response from the published Web service in Adeptia, it throws the Fault

"com.adeptia.indigo.utils.XmlException: Content is not allowed in prolog"

Cause:

The file you want to send in response has JSON in it not XML. SOAP based Web Service works in XML format only.

Solution:

If you want to send JSON in Web Service response try using Rest Provider.

For more information on Rest provider refer the below link:

http://support.adeptia.com/entries/21277367-Using-Rest-Service-as-Provider